Transcript Energy in cells

1. To know the importance of chemical energy
in biological processes
2. To understand the role of ATP
3. To draw the structure of ATP
4. To understand the stages in aerobic
respiration: glycolysis, link reaction, Kreb’s
cycle and the electron transport chain
1. Movement e.g.
movement of cilia and
flagella, muscle
contraction
2. Maintaining a constant body temperature to
provide optimum internal environment for enzymes
to function
3. Active transport – to move molecules and ions
across the cell surface membrane against a
concentration gradient
4. Anabolic processes e.g. synthesis of
polysaccharides from sugars and proteins from
amino acids
5. Bioluminescence –
converting chemical
energy into light e.g.
‘glow worms’
6. Secretion – the packaging and
transport of secretory products into
vesicles in cells e.g. in the pancreas
Respiration
 Energy is released in respiration
 A series of oxidation reactions taking place
inside living cells which releases energy to
drive the metabolic activities that take place
in cells
Aerobic respiration – takes place in the presence of
oxygen
Anaerobic respiration – takes place in absence of
oxygen
The role of ATP (adenosine triphosphate)
 The short term energy store of the cell
 Often called the ‘energy currency’ of the cell
because it picks up energy from food in
respiration and passes it on to power cell
processes.
ATP made up of:
Adenine (a base)
Ribose (a pentose
sugar)
3 phosphate groups
Draw the structure of ATP on page 286
How ATP releases energy
 The 3 phosphate groups are
joined together by 2 high
energy bonds
 ATP can be hydrolysed to
break a bond which releases
a large amount of energy
 Hydrolysis of ATP to ADP
(adenosine diphosphate) is
catalysed by the enzyme
ATPase
(ATPase)
ADP + Pi + 30 KJ mol-1
ATP
(H2O)
Draw the hydrolysis of ATP on page 286
 The 2nd phosphate group can also be
removed by breaking another high energy
bond.
 The hydrolysis of ADP to AMP (adenosine
monophosphate) releases a similar
amount of energy
(ATPase)
AMP + Pi + 30 KJ mol-1
ADP
(H2O)
AMP and ADP can be converted back to ATP by
the addition of phosphate molecules
The production of ATP
– by phosphorylation
- Adding phosphate molecules to ADP and
AMP to produce ATP
Phosphorylation is an endergonic
reaction – energy is used
Hydrolysis of ATP is exergonic - energy
is released
Advantages of ATP
 Instant source of energy in the cell
 Releases energy in small amounts as needed
 It is mobile and transports chemical energy to
where it is needed IN the cell
 Universal energy carrier and can be used in
many different chemical reactions
Answer sample past paper question on sheet
Aerobic respiration –– to release energy
4 main stages
CO2
glucose
Krebs
cycle
Glycolysis
FADH2
NADH
pyruvate
Link reaction
Electron
transport chain
Hydrogen atoms
Acetyl
coenzyme A
oxygen
water
Glycolysis -the splitting of glucose
The phosphate
comes from ATP
1. Glucose (6C)
phosphorylated to Glucose
phoshate (6C)
3. Glucose phosphate (6C)
phosphorylated to fructose
biphosphate (6C)
4. Fructose biphosphate (6C)
is split into two molecules of
glycerate 3 phosphate
5. Each Glycerate 3 –
phosphate (3C) is
converted to pyruvate
(3C)
7. 2 x 2 ATP produced
Draw glycolysis reaction on page 287
6. H+ is removed
and transferred
to the hydrogen
acceptor NAD
(nicotinamide
adenine
dinucleotide)
Glycolysis in detail
 Takes place in cytoplasm of cells
 Does not need oxygen – first stage of aerobic
respiration and only stage of anaerobic respiration
 Although glycolysis yields energy it does need an
input of energy to get the reaction started
Glycolysis – overview
Glycolysis produces from 1 molecule of
glucose:
 2 molecules of ATP in total (4 ATP are
produced but 2 are used at the start)
 2 molecules of NADH2 (reduced NAD)
 2 molecules of pyruvate to enter the link
reaction
The link reaction
in mitochondria in presence of oxygen
Pyruvate (3C)
1. Pyruvate
decarboxylated
- CO2 removed
NAD+
CO2
NADH + H+
2. Pyruvate
dehydrogenated
– hydrogen
removed
Acetate (2C)
Coenzyme A
3. Acetate (2C)
combines with
coenzyme A
Acetyl coenzyme A
Don’t forget this happens TWICE as 2 molecules of pyruvate are formed from each
glucose molecule
Krebs cycle
in matrix of mitochondria
Draw Krebs cycle on page 288